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Search Results: 1 - 10 of 3106 matches for " glass ceramics "
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Structural Changes by Thermal Treatment up to Glass Obtention of P2O5-Na2O-CaO-SiO2 Compounds with Bioglass Composition Types  [PDF]
Cristina Volzone, Franco Matías Stábile
New Journal of Glass and Ceramics (NJGC) , 2013, DOI: 10.4236/njgc.2013.31009
Abstract: P2O5-Na2O-CaO-SiO2 compounds are the base of certain glass types. Glasses are solids obtained by fast cooling of melted mix of certain compounds. Different compositions give origin to many products with a variety of applications such as: bottles, coatings, windows, tools for chemical industry, laboratory equipment, optics, as bioceramics, etc. The aim of this work was to analyze structural changes of different composition in the P2O5-Na2O-CaO-SiO2 systems thermally treated up to 1250?C, that is to say, before glass formation, by X ray diffraction. Intermediate and final developed phases up to 1100?C thermal treatment in samples were generated as a function of Na2O/CaO (1 and 1.62) and P2O5/Na2O ratios (0, 0.2 and 0.245). High-and low-combeites, calcium and sodium-calcium silicate were found at the highest studied temperature.
Research on the High Strength Glass Ceramics/Mullite Ceramics Composites  [PDF]
Yi Jun Liu, Jian Feng Huang, Xiu Feng Wang, Qiang Yang, Ya Qin Wang, Pei Wen Rao, Qing Gang Wang
New Journal of Glass and Ceramics (NJGC) , 2011, DOI: 10.4236/njgc.2011.12009
Abstract: In order to improve the bending strength of mullite ceramic thin tiles, SiO2-ZnO-Na2O-Y2O3 glass was prepared on the surface of the tiles. The influences of the thermal properties and thermal expansion coefficient of the glass and the sintering temperature on the structure and the property of the composites were investigated by differential thermal analysis (DTA), X-Ray Diffraction (XRD), Raman and scanning electron microscopy (SEM). The bending strength of the composites was measured with an universal testing machine. Results show that the crystallization temperature of the SiO2-ZnO-Na2O-Y2O3 glass is higher than that of SiO2-ZnO-Na2O glass. The corresponding crystallites show more complex structure for the SiO2-ZnO-Na2O-Y2O3 glass. The thermal expansion coefficients of both glasses are lower than the mullite ceramic tiles. The bending strength of the composites after sintering at 1150°C was obviously improved by 10.7% to 106.2 MPa, compared with the mullite ceramic tiles.
Structural Inversion and Behavioural Changes as a Function of Composition in Sr-La-Al-B-Si Based Glasses  [PDF]
Prasanta Kumar Ojha, Sangram K. Rath, Tapas K. Chongdar, Nitin M. Gokhale, Ajit R. Kulkarni
New Journal of Glass and Ceramics (NJGC) , 2011, DOI: 10.4236/njgc.2011.12004
Abstract: A series of glass sealants for solid oxide fuel cell (SOFC) with compositions SrO (x wt %) La2O3 (15 wt %) Al2O3 (15 wt %) B2O3 (40-x wt %) SiO2 (30 wt %) [x = 10, 15, 20, 25 & 30] [SLABS] have been investigated by quantitative Fourier Transform Infrared Spectroscopy (FTIR). Structural findings from FTIR reveal that with increasing substitu-tion of B2O3 by SrO, even though the B2O3/SiO2 ratio decreases, however the Si-O- non-bridging bond content in the matrix is increasing and glass structure is getting more inverted. UV-Vis Diffused Reflectance Spectroscopy (UV-Vis-DRS) of the glass series shows that electrical band gap of glasses decreases in the series from 3.07eV to 2.97eV with increasing substitution from x = 10 to x = 30. Conductivities of the glass samples were measured by AC impedance spectroscopy and found to be increasing from 2.74 × 10-5 Scm-1 to 1.09 × 10-4 Scm-1 with increasing substitution from x =10 to x = 30.
Obten??o e caracteriza??o de um vitroceramico a base de cordierita
Montedo, O. R. K.;Pereira, Y. da S.;Floriano, F. J.;Filho, J. de O.;Angioleto, E.;Bernardin, A. M.;
Matéria (Rio de Janeiro) , 2011, DOI: 10.1590/S1517-70762011000100005
Abstract: glass-ceramics are polycrystalline solids obtained by a controlled process of devitrification of glasses with composition especially prepared for this purpose. lately, glass-ceramic materials have demonstrated increasing potential of application in situations where better mechanical, chemical, and thermal performances are required. furthermore, different compositions based on cordierite have been melted, grounded, compacted, and thermally treated to produce samples that have been characterized by x-ray fluorescence spec-troscopy, x-ray diffractometry, optical dilatometry, and thermal analysis. the results showed a great potential for several applications, such as in the microelectronic industry, with features that motivate the continuity of the present study.
Crystallization Kinematics and Dielectric Behavior of (Ba,Sr)TiO3 Borosilicate Glass Ceramics  [PDF]
Avadhesh Kumar Yadav, Chandkiram Gautam, Prabhakar Singh
New Journal of Glass and Ceramics (NJGC) , 2012, DOI: 10.4236/njgc.2012.23018
Abstract: Perovskite [(Ba0.6Sr0.4)TiO3]-[2SiO2-B2O3]-[K2O]-La2O3 glass was prepared by conventional melt quench method. The differential thermal analysis (DTA) was performed on glass sample in the temperature range from 100℃ to 1000℃ by different heating rate to study the crystallization kinematics. The kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass samples were subjected to appropriate heat treatment schedules for their suitable crystallization. X-ray diffraction analysis (XRD) of glass and glass ceramic samples were done to check the amorphous state and crystalline nature. XRD of glass ceramic sample shows the major perovskite phase of BaTiO3 (BT) along with the formation of secondary phases Ba2TiSi2O8 (BTS) and Ba2Ti2B2O9 (BTB). Scanning electron microscopy (SEM) is also studied to see the morphology of the grains of major and secondary phase formation in BST glass ceramic samples. La2O3 is played an important role to increase the nucleation of the crystallites in the glassy matrix. The addition of La22O3 results in development of well interconnected crystallites formed as major phase of BST. In this paper, we are reporting the crystallization behavior of BST borosilicate glass system and high temperature dielectric characteristics of their glass ceramics.
Angular Dependence of the Second Harmonic Generation Induced by Femtosecond Laser Irradiation in Silica-Based Glasses: Variation with Writing Speed and Pulse Energy  [PDF]
Jing Cao, Bertrand Poumellec, Fran?ois Brisset, Anne-Laure Helbert, Matthieu Lancry
World Journal of Nano Science and Engineering (WJNSE) , 2015, DOI: 10.4236/wjnse.2015.53012
Abstract: To control second harmonic generation (SHG) in silica-based glasses is crucial for fabricating photonic devices, such as frequency doubling waveguides. Here, we investigated SHG of laser induced nonlinear optical crystals in silica-based glasses, according to writing speed and pulse energy. We observed two regions with different probing laser polarization angular dependence: a) a well-defined cosine-like curve with period of 180° at low pulse energy (0.8 μJ) whatever the writing speed or at high pulse energy (1.4 μJ) with high writing speed (25 μm/s). This is accounted for by a well-defined texture for the nano crystals with their polar axis oriented perpendicular to the writing laser polarization; and b) a double cosine-like curve revealing a second texture of the crystals at high pulse energy (1.4 μJ) with low writing speed (5 μm/s) and with the polar axis oriented closer parallel to the writing laser polarization. Therefore, a SHG dependence on probing laser polarization angle may show high contrast by a correct choice of the writing speed and pulse energy. These results pave the way for elaboration of nonlinear optical devices.
Influencing the Crystallization of Glass-Ceramics by Ultrashort Pulsed Laser Irradiation after Nucleation  [PDF]
Florian Senn, Ronald Holtz, Sonja-Michaela Gross-Barsnick, Uwe Reisgen
New Journal of Glass and Ceramics (NJGC) , 2018, DOI: 10.4236/njgc.2018.81001
Abstract: An ultra-fast laser with central wavelength at 1064nm and 10ps pulse durationwas used to tightly focus laser radiationwith a microscope objective inside the volume of nucleated Lithium Aluminosilicate (LAS) glass-ceramic. The nonlinear absorptionof the LAS glass-ceramic was measuredfor different laser parameters and a thermal simulation was performed to determine the temperature field inside the laser-modified area. After laser processing,the samples were crystallized in a furnace and the effect of the laser-induced modifications on the microstructure was analyzed with SEM. The SEM analysis shows an increase in the length and size of whisker-shaped?β-spodumene crystals in the laser-modified area. By increasing the dimension of these whisker-shaped crystals, the flexural strength of LAS can be improved locally.Firstfour-point bending flexural tests were performed to examine the influence on the mechanical properties.
Structural Role of Cerium Oxide in Lead Silicate Glasses and Glass Ceramics  [PDF]
Gomaa El-Damrawi, Amal Behairy
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2018, DOI: 10.4236/jmmce.2018.63031
Abstract: Silicate glasses and glass ceramics in the system CeO2-PbO-SiO2 have been studied as a function of the structure factors R and K. The latter two factors are defined as: R = (CeO2 + PbO)/SiO2 and K = (SiO2/CeO2) molar ratios. In this glass, PbO is fixed at 50 mol% and CeO2 increases at the expense of SiO2. NMR investigations have revealed that increasing R which is accompanied with decreasing K leads to reasonable decrease in the shielding of silicon atoms. The chemical shift (δ) showed an increasing behavior due to increasing non-bridging oxygen atoms (NBO) in silicate network. It is evidenced that NBO in cerium free glass is much lower than that of glasses containing CeO2. Increasing R is clearly leading to higher chemical shift and higher NBO. This reflects that CeO2 has an effective structural role, since it would be consumed in all cases as an intermediate oxide. The main portions from CeO2 and PbO inter as glass modifiers which are consumed to form NBO atoms. A limited portion of CeO2 acts as glass former which consumed to form tetrahedral cerium containing NBO due to modification by PbO as a modifier oxide. Increasing R = [(CeO2 + PbO)/SiO2] from 1 to 2.34 leads to a frequent increase of NBO in the average glass network. FTIR spectroscopy of the glasses showed a clear shift of the main absorbance peak toward the low wavenumber with increasing R which confirms the increasing silicate units containing NBO atoms. XRD of the investigated materials revealed the presence of some nanostructures from cerium silicate crystalline phases. Formation of separated phases containing micro clusters is found to depend on NBO concentration, since NBO can facilitate process of phase separation. Majority of modifier are consumed to form NBO in the glass network and the rest are aggregated or separated to form silicate phase riches with cerium cations. In such case, some of silicon atoms are electrically compensated with both Pb and Ce cations.
Structural Characterization of Novel Cerium Phosphate Glass Ionomer Cements (GICs) Doped with GaCl (Phthalocyanine)  [PDF]
Gomaa El-Damrawi, Amal Behairy, Amr M. Abdelghany
New Journal of Glass and Ceramics (NJGC) , 2018, DOI: 10.4236/njgc.2018.82003
Abstract: Cerium Pyrophosphate glass is prepared and investigated by different structural techniques. Resin modified glass ionomer cements (RGICs) of pyro cerium phosphate (40CeO2-60P2Os) composition doped with different concentrations from GaCl Phthalocyanine (C32H16ClGaN8) have been also prepared and studied for the first time. Different techniques have been applied to shed?light on the structural changes induced upon addition of GaCl-Phthalocyanine. The corresponding changes in material structure are widely approved by results of 31P magic angle spinning nuclear magnetic resonance (MAS-NMR), X-Ray diffraction and FTIR spectroscopy. The network structure of both base glass and GIC free from C32H16ClGaN8 is confirmed to be amorphous. Doping even with little concentration from GaCl-Phthalocyanine leads to changing the network structure from amorphous
Processamento e caracteriza??o de espumas vitroceramicas do sistema sncp (Sio2-Na2o-Cao-P2 O5)
Mundstock, Karoline Bastos;Moraes, Elizangela Guzi de;Hotza, Dachamir;Oliveira, Antonio Pedro Novaes de;Siligardi, Cristina;Rogero, Sizue Ota;
Química Nova , 2010, DOI: 10.1590/S0100-40422010000300021
Abstract: glass-ceramics foams prepared from glasses of the sio2-na2o-cao-p2o5 by replication process were obtained and characterized in terms of their chemical and physical properties by x-ray fluorescence, x-ray diffraction, laser diffraction, thermal analysis, density, mechanical strength, microstructural and cytotoxic analysis. the results showed that it is possible to produce glass-ceramic foams by the replication method with optimized properties but cytotoxic analysis indicates that the glass-ceramic foams are not bioactive materials. mechanical strength values varying from 0.5 to 1.0 mpa and from 0.8 to 2.3 mpa were reached for mean particle sizes of 10 and 6 μm, respectively.
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